Patent Application
20080174175
The present disclosure relates generally to master links used in machine tracks, and relates more particularly to a single tooth master link configuration and method wherein profiled sinusoidal surfaces of separate link members of the master link together define a mating interface for transmitting loads through a machine track.
Many types of machines have flexible tracks consisting of a plurality of links coupled together to form a flexible, endless loop. Conveyors, torque transmitting apparatuses and the like, for example, may utilize tracks for transporting materials or for transferring torque between rotating components. Another application for track is providing “traction” for mobile machines operating in certain environments. Mining, construction, forestry, road building and other industries all rely upon machines having ground engaging tracks for performing a variety of important tasks. As with any machine, it is desirable to provide some means for disassembling certain components for servicing or repair. A “master link” is provided in many machine tracks for this purpose, and a great many different designs have been developed over the years.
In one common class of master link designs, one or more teeth are provided on separate link portions, the link portions being mated together such that the teeth interlock with one another. Fasteners such as dowels, bolts, etc. may be used to secure the respective link portions together, and the master link positioned in a machine track where it operates much like any of the other links. When it is desirable to break the track for repair, servicing, shipping, etc., the fasteners coupling the link portions together are removed, allowing the track to be separated via disassembling the link portions. While the basic two-part master link approach has proven to be quite useful, the ruggedness of many environments within which tracked machines operate can mandate specialized features for master links, as well as place a premium on durability and service life.
As mentioned above, interlocking teeth are commonly used to couple together link portions of master links. The number, spacing, orientation, etc. of teeth in multi-piece toothed master link strategies may vary, and engineers have experimented with numerous different designs over the years. It has been discovered that in certain instances, a single tooth design provides a practical strategy, obviating the machining time requirements relating to numerous teeth, as well as having other advantages. A typical “single” tooth design actually has a tooth and pocket on each of its two link portions. The tooth of each link portion fits into the pocket of the other link portion. Fasteners are used to couple the link portions together, often slightly deforming or displacing the components to provide a snug fit and retention of the fasteners themselves.
A problem with many known single tooth and multi-tooth designs relates to the tendency for stress concentrations to be inherent in the components. Particularly where relatively complex geometry and numerous machined surfaces provide the interface between link portions of a master link, relatively sharp corners and other features can serve as stress concentrators. When actually placed in service, stress concentrations within and among the components of a master link can lead to failure after a significantly shorter service life than that of the track itself. In other words, the master link may fail before a desired time for disassembling the track, depending of course on the operating conditions. U.S. Pat. No. 4,457,565 to Bissi et al. is directed to a two-piece master link wherein a contact zone between the link portions includes a long flat, as well as relatively abrupt transitions between sections of the surfaces providing the contact zones. While Bissi et al. purport to have a design wherein all of the mating surfaces between the link portions “adhere” to one another, the design would still be susceptible to stress concentrations that could lead to unexpected failure of the master link under certain circumstances. There is thus a continuing need for improved master link durability and service life.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.
In one aspect, the present disclosure provides a master link for a track of a machine. The master link includes a first link member having a first end with a strap, a second end and a profiled surface. The profiled surface includes a first slope transitioning to a second slope via a sinusoidal segment defined by a tooth and an adjacent recess adjoining the first and second slopes, respectively. The master link further includes a second link member also having a first end with a strap, a second end and a second profiled surface which is configured complementarily to the profiled surface of the first link member. The respective profiled surfaces together define a mating interface between the first and second link members for transmitting loads between the first and second link members.
In another aspect, the present disclosure provides a machine having a frame with a plurality of rollers, a track coupled with the frame and including a plurality of links forming an endless chain extending about the rollers. The machine further includes at least one master link including one of the links of the track, the at least one master link having a first link member coupled with a second link member, each of the first and second link members including a profiled surface. The respective profiled surfaces together define a mating interface between the link members for transmitting loads through the track, each of the profiled surfaces including a first slope transitioning to a second slope via a sinusoidal segment defined by a tooth and an adjacent recess adjoining the first and second slopes, respectively.
In still another aspect, the present disclosure provides a method of reacting loads through a track of a machine, including the step of applying a load to a strap of a first link member of a master link in a track of a machine. The method further includes the step of transferring the load to a second link member of the master link via a mating interface between the first and second link members defined by first and second abutting profiled surfaces which each include a first slope transitioning with a second slope via a sinusoidal segment defined by a tooth and an adjacent recess adjoining the first and second slopes, respectively.
Referring to
Master link 20 is of the type generally known in the art as a single tooth master link, and may include a first link member 22a and a second link member 22b, each configured to couple with a separate link 16 of track 14. A ground engaging plate 21 may be coupled with one of link members 22a and 22b. Track 14 might include dual sets of coupled together links 16 extending about the respective rollers, each of the sets of links having a master link such as master link 20, although only the outermost of one of these sets of links is shown in
The ends of each of link members 22a and 22b may comprise a strap 30a and 30b which is configured to engage with and support one of a bushing and a pin (neither shown). In the illustrated embodiment, first link member 22a includes a bushing strap 30a whereas second link member 22b includes a pin strap, however, the configuration might be reversed in other embodiments. Bores 32 and 34 may be provided in each of link members 22a and 22b, respectively, for engaging with the corresponding bushing/pin, which in turn facilitate coupling with adjacent links or other track components. It should be appreciated, however, that in other embodiments, some other coupling strategy with adjacent links, or some other track configuration not using bushings or pins and the like may be implemented. In still other embodiments, each set of coupled together links 16 might include a plurality of master links.
A set of two fasteners 36 are provided for coupling link members 22a and 22b together. Fasteners 36 may be positioned within bores 38a and 38b which each extend through link member 22a and partially through link member 22b, the separate portions of bores 38a and 38b in the respective link members being configured to align with one another when link members 22a and 22b are mated together. It may be noted that in the
Each of link members 22a and 22b may include a profiled surface 50a and 50b, respectively, together defining a mating interface between link members 22a and 22b for transmitting loads between link members 22a and 22b, and consequently for transmitting loads through track 14. The respective profiled surfaces 50a and 50b may have complementary profiles, in other words as illustrated in
Profiled surface 50a may include a first slope 52 extending generally diagonally downward from second end 31a and transitioning to a second slope 54 which may be parallel with first slope 52 and extends generally diagonally upward from the vicinity of strap 30a. Transitioning of first slope 52 to second slope 54 may be via a sinusoidal segment 56 of profiled surface 50a. Sinusoidal segment 56 may be defined by a tooth 42a and a recess 40a of link member 22a. Tooth 42a and recess 40a are adjacent one another, and adjoin first slope 52 and second slope 54, respectively.
As alluded to above, profiled surfaces 50a and 50b are configured with complementary profiles and define a mating interface between link members 22a and 22b. To achieve a sound coupling between link members 22a and 22b, relatively small spaces 41 may exist between the tooth and recess of one of link members 22a and 22b and the respective recess and tooth of the other one of link members 22a and 22b. Spaces 41 may be symmetrical about centerlines C1 and C2. In one practical implementation strategy, bores 38a and 38b may span a relatively small end portion of spaces 41 at approximately a point where the corresponding slope 52, 54 transitions to a radius defined by the adjoining tooth 42a or recess 40a. This has been found to be an optimal positioning for bores 38a and 38b in at least certain embodiments, which tends to be affected by several factors. On the one hand, they cannot be located too close to straps 30a and 30b, nor can they be located too close to one another, as in either case, strength of link members 22a and 22b may be affected. Optimal positioning of bores 38a and 38b is also affected by heat treating of a rail 70, identified in
Returning to the configuration of profiled surface 50a, as used herein, the term sinusoidal should not be understood to mean that a perfect sine wave is defined by the profile of surface 50a in its sinusoidal segment, however, to achieve certain of the goals of master link 20 profiled surface 50a may have certain characteristics of a sine wave, as further described herein. In one practical implementation strategy, sinusoidal segment 56 may comprise approximately one period of a sine wave, and may comprise less than one period of a sine wave in other embodiments.
Each of tooth 42a and recess 40a may include a vertical centerline C1 and C2, as shown in
Middle segment 55, which may further include a relatively short flat, may have a profile overlapping with the radiuses defined by tooth 42a and 42b over a majority of its length. In other words, middle segment 55 may consist of a segment of profiled surface 50a which is made up predominantly by portions of profiled surface 50a which follow the radiuses of tooth 42a and recess 40a, any flat portion of middle segment 55 constituting less than a majority of its length. In other contemplated embodiments, no portion of middle segment 55 consists of a flat, and middle segment 55 will overlap the radiuses defined by tooth 42a and recess 40a along its entire length, having an inflection point at a midpoint of its length. Middle segment 55 may be blended with the radiuses defined by tooth 42a and recess 40a, respectively. Controlling the size of any flat portion of middle segment 55 as described allows the size of the radiuses defined by tooth 42a and recess 40a to be maximized, for stress distribution purposes.
Turning to
Referring also to
Turning now to
Master link 220 differs from master link 20, among other things, in that bores 238a and 238b are disposed in a side by side arrangement at the same position relative to a length L of master link 220. In addition, master link 220 includes a side lug 260 defined in part by each of link members 222a and 222b. Side lug 260 protrudes outwardly from master link 220 such that it can be engaged by a toothed rotating member of a track, such as track 14 of machine 10 shown in
Master links 20 and 220 may be suitable for use in a wide variety of tracks, however, it is contemplated they may be best suited to different track types relative to one another. Master link 20 may be used where adjacent track links are coupled together in an alternating arrangement, as will be apparent from the relative offset of straps 30a and 30b from one another. Master link 220, on the other hand, may be best suited to tracks having a different manner of coupling adjacent links together. In any event, the following description of master link 20 should be understood as generally applicable also to master link 220.
Master link 20 may be installed into a track such as track 14 for use by engaging straps 30a and 30b with pins, bushings, etc., and coupling link members 22a and 22b together via fasteners 36 such as bolts. Breaking of track 14 is achieved by loosening fasteners 36 to de-couple link members 22a and 22b, for example with wrenches, etc. Once assembled into track 14, master link 20 will tend to operate similarly to any other track link. For instance, a load applied to one of link members 22a and 22b via a strap 30a, 30b will be transmitted via the abutting profiled surfaces 50a and 50b to the other link member 22a, 22b, and thenceforth to an adjacent track link via the other strap 30a, 30b.
As discussed above, profiled surfaces 50a and 50b, and the other radial surfaces of the respective link members, are configured to distribute strain/stress during loading of master link 20 in a manner superior to known designs. This is achieved in part via sinusoidal segments 56 of the respective profiled surfaces 50a and 50a, and in particular by fashioning the radiuses defined by tooth 42a and recess 40a to be as large as possible. The footprints of each of links members 22a and 22b are also tailored to optimally distribute stress, as described herein. Earlier single tooth designs typically suffer from an inability to optimally distribute strain during loading, as the mating surfaces between the link members either include transitions, e.g. radii, which are too small, unduly concentrating stress, or because slopes in the mating surfaces are too flat, or include too much flat, to permit the radius size to be maximized. In other words, conventional single tooth master links tend to not include smoothly transitioning, symmetrical large radiuses in their abutting surfaces, or in their footprints, a characteristic which the present disclosure now recognizes as desirable in optimally distributing strain during loading. In each of the embodiments described herein, the profiled surfaces 50a, 50b, 150a, 150b, may have a uniform surface finish, at least in their respective sinusoidal segments, as load transmitting between the abutting surfaces is contemplated to be substantially uniform along the sinusoidal segments due to proper sizing, blending, etc. of the radiuses and slopes.
One example of maximizing the size of interfacing surface radiuses is in an embodiment, described above, wherein middle segment 55 of sinusoidal segment 56 overlaps with the radiuses defined by tooth 42a and recess 40a over a majority of its length, or over all of its length. By designing middle segment 55 to have a flat portion which is less than a majority of its length, or nonexistent, the relative size of the respective radiuses may be made larger. In contrast many, if not most, earlier single tooth designs include relatively large flats at the abutting surfaces between the components. The embodiments described herein enable further strain distribution by providing relatively large radiuses in transitioning from a first width of master links 20, 220 near their straps to the relatively greater width in the vicinity of bores 38a, 38b, 238a, 238b. These features all combine to create a master link superior in performance, strength and reliability than earlier designs.
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the intended spirit and scope of the present disclosure. For instance, while embodiment of
